1. Field of the Invention
The present invention relates to a scanning probe microscope and a scanning probe microscopy.
2. Description of the Related Art
A scanning probe microscope (SPM) is a generic term for scanning microscopes, which acquire information regarding the surface of a sample while scanning with a mechanical probe to map and display the information. The SPM includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), a scanning magnetic force microscope (MFM), and a scanning near field optical microscope (SNOM).
Among the SPMs, the AFM is most widely used, and comprises, as the main elements, a cantilever having a mechanical probe at its free end, an optical displacement sensor to detect the displacement of the cantilever, and a scanning mechanism to scan the mechanical probe relative to a sample. As the optical displacement sensor, an optical-lever-type optical displacement sensor is most widely used because of its high displacement detection sensitivity despite its simple construction. This optical-lever-type optical displacement sensor applies a light beam having a diameter of several, μm to several ten μm onto the cantilever, detects by, for example, a two-segment photodetector, a change of the reflection direction of the reflected light depending on the change of the curve of the cantilever, and outputs an electric signal that reflects the operation of the mechanical probe at the free end of the cantilever. The AFM scans a relative position between the mechanical probe and the sample with the scanning mechanism in the XY-directions while controlling the relative distance between the mechanical probe and the sample in a Z-direction so that the output of the optical displacement sensor is constant, thereby mapping configurations on the sample surface and then displaying the configurations on a monitor of a computer.
The AFM often uses a method (AC mode) of vibrating the cantilever and detecting, from its vibration characteristics, an interaction operating between the sample and the probe. This is attributed to such an advantage that weaker force operating between the sample and the probe can be maintained than in a normal method (called a contact mode). This AC mode AFM detects one of an amplitude change and a phase change in the vibration, that is, the displacement of the cantilever caused by the interaction operating between the sample and the probe, and measures the surface shape of the sample in accordance with the detection result.
Jpn. Pat. Appln. KOKAI Publication No. 2008-232984 discloses one of the AC mode AFMs of this type. This AC mode AFM is configured to be able to switch and detect one of the amplitude change and the phase change.